The nonlinear modeling methodology of "principal dynamic modes" (PDM) developed in Core Project #1, was applied to a spider mechanoreceptor. The fundamental question is the identification of the biophysical mechanisms that subserve mechanotransduction and the precise quantitative description of this process. The experiments (funded from other sources) employ broadband random stimuli and record either intracellularly or extracellularly. Results from the application of the PDM method to extracellular and intracellular recordings have shown excellent predictive ability of the resulting model, far exceeding the capabilities of previous models. Two PDM's have been identified in these preliminary studies, corresponding to two biophysical mechanisms: one that encodes intensity and another encoding rate of change. The latter PDM allows the mechanoreceptor to retain gain sensitivity at different operating points (adaptation). Comparisons between the results from intracellular and extracellular data were also made. This general approach can find application to other neural systems and, therefore, offers a powerful tool in a diverse and broad field of biological sciences.